I still got one electrical problem left before my first inspection over here:

When I activate the RIGHT turnsignal with my headlights ON they freeze. When I put the headlights off they start to flash again.

Also, all lamps on the LEFT side of the car lights up a little when I activate the RIGHT turnsignal.

The ground in the trunk was bad but fixed. The black cable from the battery is mounted to the engine block and was a bit loose. This cable had a very small tear in it, almost not visible. I put a piece of tape over it.

The car is a 1970 Cutlass Supreme SX 455.

 

You still have a bad ground at one of the lamp sockets. The turn signal works with the headlights off because the turn signal circuit is grounding through the parking light filament in the bulb (the 1157 bulb has two filaments connected in the bulb at a common ground). When the headlights (and thus the parking lights) are on, there is +12V on that other filament, and the turn signal circuit can no longer ground through it. Find and fix the bad ground.

 

Today I checked all the lampsockets. The two on the rear right side was bad but I fixed them and replaced all the bulbs in the rear, the two park light bulbs are also new since a few weeks ago.

I also replaced the blinker relay and the battery.
The backup lights doesnt work any of them.

Still no luck

The 1157 lamp doesnt seem available over here so everyone is using this one instead http://www.hova.com/kromad-blinkersl...92-c-1227.aspx but clear of course.

Do you have any other ideas I can check tomorrow?

 

Keep looking. It is a bad ground. Did you check the grounds for the wiring harness itself?

 

What wiring harness do you mean?

 

The one for the lights. Time to get out the wiring diagram and start checking all the grounds for the lighting circuit.

 

If I only had one

 

Register at http://wildaboutcarsonline.com

They have electronic versions of the chassis manuals with wiring diagrams free for members. I was just there and they do have the manuals for 1970

 

Very helpful site! However I didnt manage to find where the ground spots are located.
Today I found the old ground cable behind the left headlight. I connected it but no difference. I also used a separate cable and held to all the lamphousing. The grounds behind the headlights looked good too!!

Edit: Just discovered that ALL the blinkers freeze when I turn on the headlights! Do you still believe its a bad ground?

 

It's possible that you may have all of your ground connections tight but they may not be making contact because of rust and/or a painted surface that the bolt screw/bolt mounts with. I would go one-by-one with your ground connections and see if there is any paint and/or rust preventing a solid connection from happening. Things like this almost always end up being something very simple. Good luck!

 

Use a multimeter and start doing voltage drops and continuity tests to ground for the lighting circuits

 

The problem is now GONE I will do my best to explain in swenglish:

One wire was put in the wrong place behind the light switch. It probably worked somehow anyway. the light switch was very hot though.

What caused all the problems was very simple but took over 10 hours to find!!

the metal things?? inside the tail light housing wich gives the bulb power and ground were crossed behind the gasket on the backside. They only crossed when the bulb was in place.

 

yea , I got a similiar problem with my 72CS , you can wiggle the bulb back and forth in the socket on the rear bumper (upper right) and it will light up and go out as your doing that..... when I turn the lights on , the right turn signal stays lit up on the instrument panel and wont flash on & off when I apply the turn signal either , but the left works fine.....now with the lights out the left blinker flashes fine and the right blinker flashes real slow or not at all.....im thinking a ground or two along with the bad socket , because it changes every once in awhile ....probably when i hit bumps , all of a sudden it works fine for a little bit and then back to it screwing up again

 

That is exactly the sort of thing that causes these problems, and the only way to find it is to do just what you did and keep looking until you see it.

Great work! You can be proud that you found that.

- Eric

 

yet another good reason to remove battery cables every night like I do ya never when something could go wrong ....like a dead battery or worse